Content adapted with permission from the Indiana Historical Bureau, a partner in the Natural Heritage of Indiana project. More information from the Historical Bureau on the Dunes can be found here.
The dunes that march inland from the water’s edge are a record of the rise and fall of Lake Michigan over the past 10,000 years. These sands were dynamic, and ebbed and flowed with the wind. The gusts that blew in from the lake eventually sculpted a few into giants, which towered up to 200 feet tall.
But the movement and life of individual dunes weren’t permanent, as grasses and plants take root, and help to stabilize them over time. Because of the unique landscape, hundreds of miles form the nearest ocean; plants more at home along the Atlantic coast were able to thrive in the newly created dunes, as long as they, or their seeds, could first hitch a ride.
A Walk Through the Dunes
The storm beach, nearest the lake, rarely has plants. The sand however, can produce a musical tone when a person walks over it. Only a few other beaches in the world, with the same quartz sand and moisture content, have this "singing sand."
Walking away from the lake, we see the first plants beyond the reach of the highest waves. Annual plants like sea rocket and bugseed are very common. The sand-colored sand spiders, Fowler's toads, and white-footed or deer mice can be found here also.
Marram grass is one of the first dune-building plants that we see. Its special root system pushes its stems upward fast enough that blowing sand can't bury it. At the same time, it spreads out broadly to hold and stabilize the sand as it forms a dune.
The front ridges of the dunes are the youngest or most recently formed dunes. The first trees on these foredunes are usually cottonwoods, which can grow in sand, unlike most other trees which need the organic nutrients of soil to grow.
Behind the recent dunes, older sand dunes support more complex and numerous plants and animals. The back sides of many dunes face the south. More sun and protection from the wind provide a desert-like environment where even prickly pear cactus grow.
Bank swallows build their nests in eroded sand banks and hills. They are only one of over 100 species of birds living among or migrating through the Indiana Dunes.
The next trees we see after the cottonwoods are pine forests. Jack pine, red cedars, and common junipers are the most important trees on these dunes.
The Jack pine forests at the Indiana Dunes are many miles farther south than any other Jack pine forests in the Great Lakes area. The Dunes' Jack pines are left over from Indiana's glacial past. The bearberry, also a cold climate plant, grows in the pine forests. Its low, woody growth protects the young Jack pine seedlings from wind and blowing sand.
Ponds, swamps, marshes, and bogs are also part of the Dunes' ecology. These wetlands contain many rare and beautiful plants and animals.
Tamaracks are special trees associated with bogs. Tamaracks are conifers like pine trees, but their needles turn yellow and fall every year like maples or other deciduous trees.
Some bog plants like the sundew, trap and eat insects. The sundew's round leaves are covered with hairs. The ends of the hairs are sticky. when an insect lands on a leaf, it gets stuck, and the leaf closes around it and eventually digests it.
Other plants grow so densely in the shallow swamps that they can support the weight of a human, Sphagnum moss and sedge are such plants.
As we move farther inland, forests of oak trees appear on the dunes. These older dunes have accumulated enough soil to support more complex root systems. Moving farther, we see that the oldest dunes are heavily forested with beech and maple trees.